Automatic tire loading mechanisms or loaders have been employed in connection with the introduction of green tires into the tire molds or cavities of tire presses. Perhaps the most common type of loader employed today is that which picks up a green tire by the top bead thereof from a loading stand in front of the press and then horizontally shifts the green tire into axial alignment with the lower mold section of the press and, in some instances, also with the upper mold section. Some loaders of this general type then would deposit the green tire onto the lower mold section as by placement or dropping and, thereafter, would move clear of the press for subsequent bladder insertion and shaping of the green tire and press closure, whereas other loaders would continue to hold the green tire during the bladder insertion and initial shaping operation and then move clear of the press to permit press closure.
Examples of tire loaders of the foregoing general type can be seen in Ulm et al U.S. Pat. No. 3,584,335, Barton U.S. Pat. No. 3,924,983, Nakagawa et al U.S. Pat. No. 4,035,117 and Yuhas et al U.S. Pat. No. 4,092,090. The loaders illustrated in these patents generally constitute press attachments, whereas in Turk et al U.S. Pat. Nos. 3,350,533 and 3,378,882, loaders employing expandable plate-type or finger chucks are built into the movable upper half or head of the press. While having advantages over other press loader arrangements, the latter arrangement is relatively energy inefficient since the entire press head must be shuttled laterally between the pick-up and load positions. This would be of greater consequence in connection with the loading and curing of large tires such as truck tires, and the correspondingly larger and heavier press heads. Also, the lateral shuttling of such larger and heavier press heads may present significant alignment and wear problems.
Tire press loaders also are known to pick up a green tire by the tread thereof rather than by the top bead. An example of this general type of loader can be seen in Getz U.S. Pat. No. 3,790,656. Where outside or basket loaders have been employed, such devices usually comprise vertically elongated and heavy shoes which tend to distort the tire and which are not suitable for placement between axially separated mold sections.
One problem encountered heretofore with known loaders and presses and associated methods has been the inability to load efficiently, automatically and repeatedly the green tires into the press with assurance that the green tire is properly located in the press before and during bladder insertion and shaping. The problem at least partly stems from the fact that the sidewalls of preshaped green tires may be quite flexible and may also become dimensionally distorted in storage while awaiting cure. Since most automatic loaders used today pick up the green tire by the top head thereof, there is no assurance that other portions of the green tire will be in a known or given location relative to the bladder before and during insertion. Moreover, the green tire may be pushed off center by the bladder as the bladder is inserted into the green tire. As a result, there is the likelihood of asymmetrical positioning of the green tire in relation to the bladder and press mold. This problem is of even greater consequence in connection with the loading of large tires such as truck tires.
Another and related concern associated with tire press loaders and press loading methods, regardless of type of loader employed, has been the need to insure proper positioning and seating of the green tire beads on respective bead seats or rings provided in or in conjunction with the upper and lower mold sections of the press. For the most part, common practice in presses employing shaping and curing bladders has been to use the bladder to effect final seating of the green tire beads. As shown in Gazuit U.S. Pat. No. 3,837,770, for example, the top and bottom beads of the green tire, prior to bladder inflation and manipulation, are relatively loosely supported by the respective bead seats of the press mold in the then substantially closed press. When the bladder is inflated into the green tire, the beads are finally seated by the bladder on the bead seats.
One problem with this common practice is that any existing asymmetry between the bladder, green tire beads and bead seats or rings during bead seating may result in bead kinks or otherwise improper positioning or seating of the beads. Even if full seating of the beads is achieved, any correction of misalignment existing prior to bladder shaping may result in the inducement of irregular assymetrical molding stresses in the bead area of the tire after final shaping and cure. These problems are of even greater concern when loading preshaped tires which, as above indicated, may have relatively flimsy sidewalls that may become dimensionally distorted in shape while awaiting cure, this increasing the likelihood of assymetrical positioning of the green tire beads in relation to the bladder and the bead rings or seats.
Several attempts have been made to achieve proper positioning and seating of at least one of the green tire beads. One attempt is disclosed in Gazuit U.S. Pat. No. 3,794,457 wherein a small tubular, inflatable bladder is used to seat the bottom tire bead of the green tire against the lower bead ring of a press prior to tire shaping by the shaping and curing bladder. When not in use such as during tire cure, the bead positioning device is telescoped into or housed in a well in the lower half of the press. As disclosed in such patent, the bead positioning and centering device may be associated with the upper mold of the press and used for positioning and centering the top bead of the tire around the upper bead ring of the press.
Another attempt toward solution of the bead positioning problem is disclosed in Gazuit U.S. Pat. No. 4,045,150 wherein a top bead positioning device employs a circular set of radially expandable segments or fingers to center the top bead of the green tire to the upper bead ring. Such a device is somewhat of an off-shoot of the loader/press combination disclosed in the aforementioned Turk et al U.S. Pat. No. 3,378,882, although the green tire is first placed on the lower mold portion of the press as by an automatic loader and then the upper mold portion lowered for subsequent operation of the positioning device. In either arrangement, final seating of the top bead of the green tire is effected by the shaping and curing bladder, such being inserted into the green tire and inflated to push the top bead of the green tire onto the upper bead ring.
Presses of the bladderless type, by their nature, do not effect bead seating by means of a shaping and curing bladder. Instead, final seating of the beads may be effected by bead clamps employed in these presses and to some extent by the admission of pressurized air into the tire for initial shaping thereof. Also, in the retreading art, direct application of air pressure to the tire may be employed at least in part for bead seating. Examples of a bladderless press and retread machine can be seen in Turk et al U.S. Pat. No. 4,236,883 and Barefoot U.S. Pat. No. 3,816,217, respectively. Moreover, it is common practice directly to inflate cured tires installed on rims and the like such as during post-cure inflation or in connection with final use applications.
Automatic tire unloading mechanisms or unloaders also have been employed to effect removal of cured tires from tire presses. Typically, such unloaders operate to remove the cured tires to the rear of the presses while green tires are loaded from the front of the presses. Examples of known unloaders can be seen in Singh U.S. Pat. No. 4,170,442 and Singh et al U.S. Pat. No. 4,332,536. The unloader also may be built into the movable head of the press as seen in Yuhas U.S. Pat. No. 4,092,090.